Polyaxial bone anchor with pop-on shank, shank, friction fit retainer, winged insert and low profile edge lock

ABSTRACT

A polyaxial bone screw assembly includes a threaded shank body having an integral upper portion receivable in an integral receiver, the receiver having an upper channel for receiving a longitudinal connecting member and a lower cavity cooperating with a lower opening. A down-loadable compression insert, a down-loadable friction fit split retaining ring having inner and outer tangs and an up-loadable shank upper portion cooperate to provide for pop- or snap-on assembly of the shank with the receiver either prior to or after implantation of the shank into a vertebra. The shank and receiver once assembled cannot be disassembled.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication Ser. No. 61/627,374 filed Oct. 11, 2011 that is incorporatedby reference herein.

This application is also a continuation-in-part of U.S. patentapplication Ser. No. 13/573,516 filed Sep. 19, 2012 that claims thebenefit of U.S. Provisional Patent Application Ser. No. 61/626,250 filedSep. 23, 2011, both of which are incorporated by reference herein. Thisapplication is also a continuation-in-part of U.S. patent applicationSer. No. 13/573,303 filed Sep. 7, 2012 that claims the benefit of U.S.Provisional Patent Application Ser. No. 61/573,508 filed Sep. 7, 2011,both of which are incorporated by reference herein. This application isalso a continuation-in-part of U.S. patent application Ser. No.13/506,365 filed Apr. 13, 2012 that claims the benefit of U.S.Provisional Patent Application Ser. No. 61/517,088 filed Apr. 13, 2011,both of which are incorporated by reference herein. This application isalso a continuation-in-part of U.S. patent application Ser. No.13/385,212 filed Feb. 8, 2012 that claims the benefit of U.S.Provisional Patent Application Ser. No. 61/463,037 filed Feb. 11, 2011,both of which are incorporated by reference herein. This application isalso a continuation-in-part of U.S. patent application Ser. No.13/374,439 filed Dec. 29, 2011 is incorporated by reference herein. U.S.patent application Ser. No. 13/374,439 claims the benefit of U.S.Provisional Patent Application Ser. No. 61/460,267, filed Dec. 29, 2010and U.S. Provisional Patent Application Ser. No. 61/463,037, filed Feb.11, 2011. This application is also an continuation-in-part of U.S.patent application Ser. No. 13/373,289, filed Nov. 9, 2011 that claimsthe benefit of U.S. Provisional Patent Application Ser. No. 61/456,649filed Nov. 10, 2010 and Provisional Patent Application Ser. No.61/460,234 filed Dec. 29, 2010, all of which are incorporated byreference herein. This application is also a continuation-in-part ofU.S. patent application Ser. No. 13/136,331 filed Jul. 28, 2011 thatclaims the benefit of U.S. Provisional Patent Application Ser. No.61/400,504 filed Jul. 29, 2010, and 61/403,915 filed Sep. 23, 2010, allof which are incorporated by reference herein. This application is alsoa continuation-in-part of U.S. patent application Ser. No. 12/924,802filed Oct. 5, 2010 that claims the benefit of the following U.S.Provisional Patent Application Ser. No. 61/278,240, filed Oct. 5, 2009;61/336,911, filed Jan. 28, 2010; 61/343,737 filed May 3, 2010;61/395,564 filed May 14, 2010; 61/395,752 filed May 17, 2010; 61/396,390filed May 26, 2010; 61/398,807 filed Jul. 1, 2010; 61/400,504 filed Jul.28, 2010; 61/402,959 filed Sep. 8, 2010; 61/403,696 filed Sep. 20, 2010;and 61/403,915 filed Sep. 23, 2010, all of which are incorporated byreference herein. This application is also a continuation-in-part ofU.S. patent application Ser. No. 12/802,849 filed Jun. 15, 2010 thatclaims the benefit of the following U.S. Provisional Patent ApplicationSer. No. 61/268,708 filed Jun. 15, 2009; 61/270,754, filed Jul. 13,2009; 61/336,911 filed Jan. 28, 2010; 61/395,564 filed May 14, 2010;61/395,752 filed May 17, 2010; and 61/396,390 filed May 26, 2010, all ofwhich are incorporated by reference herein.

BACKGROUND OF THE INVENTION

The present invention is directed to polyaxial bone screws for use inbone surgery, particularly spinal surgery and particularly to suchscrews with compression or pressure inserts and expansion lock splitretainers to snap over, capture and retain the bone screw shank head inthe receiver member assembly and later fix the bone screw shank withrespect to the receiver assembly.

Bone screws are utilized in many types of spinal surgery in order tosecure various implants to vertebrae along the spinal column for thepurpose of stabilizing and/or adjusting spinal alignment. Although bothclosed-ended and open-ended bone screws are known, open-ended screws areparticularly well suited for connections to rods and connector arms,because such rods or arms do not need to be passed through a closedbore, but rather can be laid or urged into an open channel within areceiver or head of such a screw. Generally, the screws must be insertedinto the bone as an integral unit along with the head, or as apreassembled unit in the form of a shank and pivotal receiver, such as apolyaxial bone screw assembly.

Typical open-ended bone screws include a threaded shank with a pair ofparallel projecting branches or arms which form a yoke with a U-shapedslot or channel to receive a rod. Hooks and other types of connectors,as are used in spinal fixation techniques, may also include similar openends for receiving rods or portions of other fixation and stabilizationstructure.

A common approach for providing vertebral column support is to implantbone screws into certain bones which then in turn support a longitudinalstructure such as a rod, or are supported by such a rod. Bone screws ofthis type may have a fixed head or receiver relative to a shank thereof,or may be of a polyaxial screw nature. In the fixed bone screws, the rodreceiver head cannot be moved relative to the shank and the rod must befavorably positioned in order for it to be placed within the receiverhead. This is sometimes very difficult or impossible to do. Therefore,polyaxial bone screws are commonly preferred. Open-ended polyaxial bonescrews typically allow for a loose or floppy rotation of the head orreceiver about the shank until a desired rotational position of thereceiver is achieved by fixing such position relative to the shankduring a final stage of a medical procedure when a rod or otherlongitudinal connecting member is inserted into the receiver, followedby a locking screw or other closure. This floppy feature can be, in somecases, undesirable and make the procedure more difficult. Also, it isoften desirable to insert the bone screw shank separate from thereceiver or head due to its bulk which can get in the way of what thesurgeon needs to do. Such screws that allow for this capability aresometimes referred to as modular polyaxial screws.

With specific reference to modular snap-on or pop-on polyaxial pediclescrew systems having shank receiver assemblies, the prior art has shownand taught the concept of the receiver and certain retainer partsforming an assembly wherein a contractile locking engagement between theparts is created to fix the shank head with respect to the receiver andretainer. The receiver and shank head retainer assemblies in the priorart have included a slotted contractile retainer ring and/or a lowerpressure slotted insert with an expansion and contraction collet-type ofstructure having contractile locking engagement for the shank head dueto direct contact between the retainer and/or the collet structure withthe receiver resulting in contraction of the slotted retainer ringand/or the collet-type structure of the insert against the shank head.The receiver and slotted insert have generally included tapered lockingengagement surfaces.

The prior art for modular polyaxial screw assemblies has also shown andtaught that the contact surfaces on the outside of the slotted colletand/or retainer and the inside of the receiver, in addition to beingtapered, can be conical, radiused, spherical, curvate, multi-curvate,rounded, as well as other configurations to create a contractile type oflocking engagement for the shank head with respect to the receiver.

In addition, the prior art for modular polyaxial screw assemblies hasshown and taught that the shank head can both enter and escape from acollet-like structure on the insert or from the retainer when the insertor retainer is in the up position and within an expansion recess orchamber of the receiver. This is the case unless the slotted insertand/or the slotted retainer are blocked or constrained from being ableto be pushed or manipulated back up into the receiver bore or cavity, orunless the screw assemblies are otherwise uniquely configured to preventthis from happening.

SUMMARY OF THE INVENTION

The present invention differentiates from the prior art by not allowingthe receiver to be removed from the shank head once the parts aresnapped-on and connected. This is true even if the retainer can go backup into the expansion chamber. This approach or design has been found tobe more secure and to provide more resistance to pull-out forcescompared to the prior art for modular polyaxial screw designs.Collect-like structures extending downwardly from lower pressureinserts, when used in modular polyaxial screw designs, as shown in theprior art, have been found to be somewhat weak with respect to pull-outforces encountered during some spinal reduction procedures.

Embodiments of the present invention also differentiate from the priorart by providing a split retainer ring with inner friction fit surfacesthat may be partially radiused that do not participate in the finallocking engagement for the shank head with respect to the receiver. Inaddition, the retainer ring itself is uniquely characterized by a baseportion providing expansion to receive and capture the shank head andthen having expansion (not contraction) locking engagement between theshank head and the retainer ring base and between the retainer ring baseand horizontal and vertical loading surfaces near a bottom opening ofthe receiver.

The expansion-only retainer ring base portion is positioned entirelybelow the shank head hemisphere in the receiver and can be a stronger,more substantial structure to resist larger pull out forces on theassembly. The retainer ring base can also be better supported on agenerally horizontal loading surface near the lower opening in thebottom of the receiver. This design has been found to be stronger andmore secure when compared to that of the prior art which uses some typeof contractile locking engagement between the parts, as described above;and, again, once assembled it cannot be disassembled.

Thus, an embodiment of a polyaxial bone screw assembly according to theinvention includes a shank having an integral upper portion or integralradiused or spherical head and a body for fixation to a bone; a separatereceiver defining an upper open channel, a central bore, a lower cavityand a lower opening; a top drop and turn in place lower compressioninsert; and a friction fit resilient expansion locking split retainerfor capturing the shank head in the receiver lower cavity, the shankhead being frictionally engaged with, but still movable in a non-floppymanner with respect to the friction fit retainer and the receiver priorto locking of the shank into a desired configuration. The shank isfinally locked into a fixed position relative to the receiver byfrictional engagement between the insert and a lower split ring-likeportion of the retainer, as described previously, due to a downwardforce placed on the compression insert by a closure top pressing on arod, or other longitudinal connecting member, captured within thereceiver bore and channel. In the illustrated embodiments, retainers andcompression inserts are downloaded into the receiver, but uploadedembodiments are also foreseen. The shank head can be positioned into thereceiver lower cavity at the lower opening thereof prior to or afterinsertion of the shank into bone. In some embodiments, the compressioninsert may include a lock and release feature for independent locking ofthe polyaxial mechanism so the screw can be used like a fixed monoaxialscrew. Also, in some embodiments, the shank (as well as other componentsof the assembly, including the closure top) can be cannulated forminimally invasive surgery applications. The retainer includes upwardlyextending tangs that are deployed in the receiver cavity so that theretainer and captured shank head are stabilized and retained in theregion of the receiver locking chamber once, but are free to rotatewithin the cavity. In this way, the shank head and retainer arepartially constrained and cannot go back up into the receiver cavity,but can be manipulated there-within.

Again, a pre-assembled receiver, compression insert and friction fitsplit retainer may be “pushed-on”, “snapped-on” or “popped-on” to theshank head prior to or after implantation of the shank into a vertebra.Such a “snapping on” procedure includes the steps of uploading the shankhead into the receiver lower opening, the shank head pressing againstthe base portion of the split retainer ring and expanding the resilientlower open retainer portion out into an expansion portion or chamber ofthe receiver cavity followed by an elastic return of the retainer backto a nominal or near nominal shape thereof after the hemisphere of theshank head or upper portion passes through the lower ring-like portionof the retainer. The shank head enters into friction fit engagement withportions of the retainer, defined at least in part, by inner tangs ofthe retainer. The retainer snapping onto the shank head as the retainerreturns to a neutral or close to neutral orientation, providing anon-floppy connection between the retainer and the shank head. In theillustrated embodiments, when the shank is ultimately locked between thecompression insert and the lower portion of the retainer, at least onelower, inner retainer edge surface locks against the shank head. Thefinal fixation occurs as a result of a locking expansion-type of contactbetween the shank head and the lower edge portion of the split retainerand an expansion-type of non-tapered locking engagement between thelower portion of the retainer ring and the locking chamber in the lowerportion of the receiver cavity. The retainer can expand more in theupper portion or expansion chamber of the receiver cavity to allow theshank head to pass through, but has restricted expansion to retain theshank head when the retainer lower ring portion is against the lockingchamber surfaces in the lower portion of the receiver cavity and theshank head is forced down against the retainer ring during finallocking. In some embodiments, when the polyaxial mechanism is locked,the pressure or compression insert is forced or wedged against a surfaceof the receiver resulting in an interference locking engagement,allowing for adjustment or removal of the rod or other connecting memberwithout loss of a desired angular relationship between the shank and thereceiver. This independent locking feature allows the polyaxial screw tofunction like a fixed monoaxial screw.

The lower pressure insert may also be configured to be independentlylocked by a tool or instrument, thereby allowing the pop-on polyaxialscrew to be distracted, compressed and/or rotated along and around therod to provide for improved spinal correction techniques. Such a toolengages the receiver from the sides and then engages outwardly extendingwinged arms of the insert to force or wedge the insert down into alocked position within the receiver. With the tool still in place andthe correction maintained, the rod is then locked within the receiverchannel by a closure top followed by removal of the tool. This processmay involve multiple screws all being manipulated simultaneously withmultiple tools to achieve the desired correction.

Objects of the invention further include providing apparatus and methodsthat are easy to use and especially adapted for the intended use thereofand wherein the tools are comparatively inexpensive to produce. Otherobjects and advantages of this invention will become apparent from thefollowing description taken in conjunction with the accompanyingdrawings wherein are set forth, by way of illustration and example,certain embodiments of this invention.

The drawings constitute a part of this specification and includeexemplary embodiments of the present invention and illustrate variousobjects and features thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view of a polyaxial bone screwassembly of an embodiment according to the present invention including ashank, a receiver, an open friction fit retainer and a top drop and turnin place lower compression insert, further shown with a portion of alongitudinal connecting member in the form of a rod and a closure top.

FIG. 2 is an enlarged top plan view of the shank of FIG. 1.

FIG. 3 is a reduced cross-sectional view taken along the line 3-3 ofFIG. 2.

FIG. 4 is an enlarged side elevational view of the receiver of FIG. 1.

FIG. 5 is a perspective view of the receiver of FIG. 4.

FIG. 6 is a front elevational view of the receiver of FIG. 4.

FIG. 7 is a bottom plan view of the receiver of FIG. 4.

FIG. 8 is a top plan view of the receiver of FIG. 4.

FIG. 9 is a cross-sectional view taken along the line 9-9 of FIG. 8.

FIG. 10 is a cross-sectional view taken along the line 10-10 of FIG. 8.

FIG. 11 is an enlarged perspective view of the retainer of FIG. 1.

FIG. 12 is a reduced front elevational view of the retainer of FIG. 11.

FIG. 13 is a reduced bottom plan view of the retainer of FIG. 11.

FIG. 14 is a top view of the retainer of FIG. 11.

FIG. 15 is a reduced bottom perspective view of the retainer of FIG. 11.

FIG. 16 is an enlarged cross-sectional view taken along the line 16-16of FIG. 14.

FIG. 17 is an enlarged perspective view of the insert of FIG. 1.

FIG. 18 is a side elevational view of the insert of FIG. 17.

FIG. 19 is another perspective view of the insert of FIG. 17.

FIG. 20 is a top plan view of the insert of FIG. 17.

FIG. 21 is a bottom plan view of the insert of FIG. 17.

FIG. 22 is an enlarged cross-sectional view taken along the line 22-22of FIG. 20.

FIG. 23 is an enlarged cross-sectional view taken along the line 23-23of FIG. 20.

FIG. 24 is an enlarged front elevational view of the retainer andreceiver of FIG. 1 with portions of the receiver broken away to show thedetail thereof, the retainer being shown downloaded into the receiver(in phantom) to a tipped, partially inserted stage of assembly.

FIG. 25 is a front elevational view of the retainer and receiver withportions broken away, similar to what is shown in FIG. 24, showing theretainer in a subsequent stage of assembly and in a maximum state ofcompression.

FIG. 26 is an enlarged and partial bottom perspective view of thereceiver and retainer of FIG. 25.

FIG. 27 is an enlarged front elevational view of the retainer andreceiver with portions broken away, similar to what is shown in FIG. 25,showing the retainer positioned lower in the receiver cavity and furthershows the inert in position for assembly with the receiver.

FIG. 28 is an enlarged front elevational view of the retainer, receiverand insert with portions broken away, similar to what is shown in FIG.27, further showing the insert being downloaded into the receiver to alocation suitable for rotation within the receiver.

FIG. 29 is a reduced front elevational view of the retainer, receiverand insert, similar to what is shown in FIG. 28, further showing theinsert being partially rotated within the receiver.

FIG. 30 is an enlarged perspective view of the retainer, receiver andinsert of FIG. 29, showing the insert rotated into a desired positionfor assembly with the shank of FIG. 1 and showing the receiver crimpedagainst the insert.

FIG. 31 is a reduced front elevational view of the assembly of FIG. 30,the figure further showing the shank of FIG. 1 in a partial frontelevational view and implanted into a portion of a vertebra, ahemisphere of the shank head and the vertebra portion are both shown inphantom.

FIG. 32 is an enlarged and partial front elevational view with portionsbroken away, similar to FIG. 31, and further showing the shank in afirst stage of assembly with the receiver and retainer.

FIG. 33 is an enlarged and partial front elevational view with portionsbroken away, similar to FIG. 32, showing the retainer lower portion inan expanded state about a mid-portion of the shank head.

FIG. 34 is a reduced and partial front elevational view with portionsbroken away, similar to FIG. 33, the spherical shank upper portion orhead shown fully captured by the retainer.

FIG. 35 is an enlarged and partial front elevational view with portionsbroken away, similar to FIG. 34, the shank upper portion with attachedretainer being shown pulled down into a seated position within the lowerreceiver cavity, the retainer spring tabs in a substantially neutralstate, extending outwardly and captured beneath a surface of thereceiver, further shown is the rod and closure top of FIG. 1, also shownin an enlarged and partial front elevational view with portions brokenaway to show the detail thereof.

FIG. 36 is a reduced and partial front elevational view with portionsbroken away, similar to FIG. 35, the shank being shown in a maximumpossible push upped position prior to locking with the rod and closuretop.

FIG. 37 is a reduced and partial front elevational view with portionsbroken away, similar to FIG. 35, the insert being shown pushed down intoa fully seated position within the lower receiver cavity by pressurebeing placed thereon from above by the rod and closure top, the insertbeing placed in locking interference fit with the receiver.

FIG. 38 is a reduced and partial front elevational view with portionsbroken away, similar to FIG. 37, but with the rod and closure topremoved, the locking insert keeping the shank locked in place, thefigure further showing an alternative locking insert, a deformable rodand cooperating closure top being installed in the receiver.

FIG. 39 is an enlarged and partial front elevational view with portionsbroken away, similar to FIG. 38, showing the alternative rod and closuretop fixed to the receiver.

FIG. 40 is a reduced side elevational view of the assembly of FIG. 1,shown fully assembled with the shank disposed at an eighteen degree(cephalad) angle with respect to the receiver.

FIG. 41 is an enlarged perspective view of the assembly of FIG. 40.

FIG. 42 is an enlarged and partial side elevational view of the assemblyof FIG. 40 with portions broken away to show the detail thereof.

FIG. 43 is a reduced side elevational view of the assembly of FIG. 1,shown fully assembled with the shank disposed at a thirty degree(caudad) angle with respect to the receiver.

FIG. 44 is an enlarged perspective view of the assembly of FIG. 43.

FIG. 45 is an enlarged and partial side elevational view of the assemblyof FIG. 43 with portions broken away to show the detail thereof.

FIG. 46 is an enlarged perspective view of an alternative retainer foruse in lieu of the retainer in the assembly of FIG. 1.

FIG. 47 is another perspective view of the retainer of FIG. 46.

FIG. 48 is en enlarged bottom plan view of the retainer of FIG. 46.

FIG. 49 is a cross-sectional view taken along the line 49-49 of FIG. 48.

FIG. 50 is an enlarged and partial side elevational view of the assemblyof FIG. 1 modified to include the retainer of FIG. 46 in lieu of theretainer shown in FIG. 1, and shown with portions broken away to showthe detail thereof.

FIG. 51 is an enlarged perspective view of an alternative extended orfavored angle receiver of an embodiment according to the inventionhaving opposed lower concave surfaces for cooperating with the retainerof FIG. 1 to allow for up to a forty degree angle of the shank of FIG. 1with respect to the alternative receiver.

FIG. 52 is an enlarged bottom plan view of the alternative receiver ofFIG. 51.

FIG. 53 is an enlarged perspective view of the assembly of FIG. 1modified to include the alternative receiver of FIG. 51 in lieu of thereceiver shown in FIG. 1.

FIG. 54 is an enlarged and partial front elevational view of theassembly of FIG. 53 with portions broken away to show the detailthereof.

FIG. 55 is a perspective view of another alternative extended or favoredangle embodiment of a receiver according to the invention, similar tothe receiver of FIG. 51, but having lower concave stepped surfaces.

FIG. 56 is an enlarged and partial front elevational view of theassembly of FIG. 1 modified to include the alternative receiver of FIG.55 in lieu of the receiver shown in FIG. 1.

FIG. 57 is an enlarged perspective view of an alternative non-lockingembodiment of an insert according to the invention for use in lieu ofthe locking insert shown in FIG. 1.

FIG. 58 is an enlarged front elevational view of the receiver andretainer of FIG. 1 shown in a stage of assembly with the alternativeinsert of FIG. 57, also in front elevation, with portions broken away toshow the detail thereof.

FIG. 59 is an enlarged and partial front elevational view of thereceiver, retainer, rod and closure top of FIG. 1 shown fully assembledwith the alternative insert of FIG. 57, also in front elevation, withportions broken away to show the detail thereof.

DETAILED DESCRIPTION OF THE INVENTION

As required, detailed embodiments of the present invention are disclosedherein; however, it is to be understood that the disclosed embodimentsare merely exemplary of the invention, which may be embodied in variousforms. Therefore, specific structural and functional details disclosedherein are not to be interpreted as limiting, but merely as a basis forthe claims and as a representative basis for teaching one skilled in theart to variously employ the present invention in virtually anyappropriately detailed structure. It is also noted that any reference tothe words top, bottom, up and down, and the like, in this applicationrefers to the alignment shown in the various drawings, as well as thenormal connotations applied to such devices, and is not intended torestrict positioning of the bone attachment structures in actual use.

With reference to FIGS. 1-45, the reference number 1 generallyrepresents an embodiment of a polyaxial bone screw apparatus or assemblyaccording to the present invention. The assembly 1 includes a shank 4,that further includes a body 6 integral with an upwardly extending upperportion or head 8; a receiver 10; a friction fit retainer 12, and acrown-like compression or pressure insert 14. The receiver 10, retainer12 and compression insert 14 are initially assembled and may be furtherassembled with the shank 4 either prior or subsequent to implantation ofthe shank body 6 into a vertebra 17, as will be described in greaterdetail below. FIGS. 1 and 35-37 further show a closure structure 18 forcapturing a longitudinal connecting member, for example, a rod 21 whichin turn engages the compression insert 14 that presses against the shankhead 8 into fixed frictional contact with the retainer 12, so as tocapture, and fix the longitudinal connecting member 21 within thereceiver 10 and thus fix the member 21 relative to the vertebra 17. Thereceiver 10 and the shank 4 cooperate in such a manner that the receiver10 and the shank 4 can be secured at any of a plurality of angles,articulations or rotational alignments relative to one another andwithin a selected range of angles both from side to side and from frontto rear, to enable flexible or articulated engagement of the receiver 10with the shank 4 until both are locked or fixed relative to each othernear the end of an implantation procedure. The illustrated rod 21 ishard, stiff, non-elastic and cylindrical, having an outer cylindricalsurface 22. In some embodiments, the rod 21 may be elastic, deformableand/or of different materials and cross-sectional geometries (see, e.g.,FIGS. 38 and 39). As shown in FIG. 39, in some embodiments of theinvention, the closure top presses directly on the insert 14, forexample, when the rod is deformable.

The shank 4, best illustrated in FIGS. 1-3, is elongate, with the shankbody 6 having a helically wound bone implantable thread 24 (single ordual lead thread form and different thread types) extending from near aneck 26 located adjacent to the upper portion or head 8, to a tip 28 ofthe body 6 and extending radially outwardly therefrom. During use, thebody 6 utilizing the thread 24 for gripping and advancement is implantedinto the vertebra 17 leading with the tip 28 and driven down into thevertebra with an installation or driving tool (not shown), so as to beimplanted in the vertebra to a location at or near the neck 26, as shownin FIG. 31, for example, and more fully described in the paragraphsbelow. The shank 4 has an elongate axis of rotation generally identifiedby the reference letter A.

The neck 26 extends axially upward from the shank body 6. The neck 26may be of the same or is typically of a slightly reduced radius ascompared to an adjacent upper end or top 32 of the body 6 where thethread 24 terminates. Further extending axially and outwardly from theneck 26 is the shank upper portion or head 8 that provides a connectiveor capture apparatus disposed at a distance from the upper end 32 andthus at a distance from the vertebra 17 when the body 6 is implanted insuch vertebra.

The shank upper portion 8 is configured for a pivotable connectionbetween the shank 4 and the retainer 12 and receiver 10 prior to fixingof the shank 4 in a desired position with respect to the receiver 10.The shank upper portion 8 has an outer, convex and substantiallyspherical surface 34 that extends outwardly and upwardly from the neck26 that terminates at a substantially annular, planar rim surface 38that is perpendicular to the shank central axis A. In some embodiments,a frusto-conical surface extends from the spherical surface 34 inwardlyto the top surface 38, providing additional clearance during pivoting ofthe shank with respect to the receiver 10 and the insert 14. Thespherical surface 34 has an outer radius configured for temporaryfrictional, non-floppy, sliding cooperation with one or more edgesand/or surfaces of the retainer 12, as well as ultimate frictionalengagement with the retainer 12 at, at least one lower inner edgethereof and ultimate frictional engagement with the insert 14 at aninner partially spherical surface thereof and/or stepped or ridgedsurfaces thereof, as will be discussed more fully in the paragraphsbelow. In FIG. 1 and some of the other figures, a dotted line 40designates a hemisphere of the spherical surface 34. The sphericalsurface 34 shown in the present embodiment is substantially smooth, butin some embodiments may include a roughening or other surface treatmentand is sized and shaped for cooperation and ultimate frictionalengagement with the compression insert 14 as well as ultimate frictionalengagement with a lower ring-like edge of the retainer 12. The shankspherical surface 34 is locked into place exclusively by the insert 14and the retainer 12 lower edged portion and not by inner surfacesdefining the receiver cavity.

A counter sunk and stepped or graduated annular seating surface or base45 partially defines a portion of an internal drive feature or imprint46. In some embodiments of the invention, the surface 45 issubstantially planar. The illustrated internal drive feature 46 is anaperture formed in the top 38 and has a hex shape designed to receive atool (not shown) of an Allen wrench type, into the aperture for rotatingand driving the bone screw shank 4 into the vertebra 17. It is foreseenthat such an internal tool engagement structure may take a variety oftool-engaging forms and may include one or more apertures of variousshapes, such as a pair of spaced apart apertures or a multi-lobular orstar-shaped aperture. The graduated seat or base surfaces 45 of thedrive feature 46 are disposed substantially perpendicular to the axis Awith the drive feature 46 otherwise being coaxial with the axis A. Asillustrated in FIGS. 2 and 3, the drive seat 45 having beveled orstepped surfaces advantageously further enhances gripping with thedriving tool. In operation, the driving tool (not shown) is received inthe internal drive feature 46, being seated at the base 45 and engagingthe faces of the drive feature 46 for both driving and rotating theshank body 6 into the vertebra 17, either before or after the shank 4 isconnected to the receiver 10 via the retainer 12, the driving toolextending into the receiver 10 when the shank 4, retainer 12 andreceiver 10 combination is driven into the vertebra 17.

The shank 4 shown in the drawings is cannulated, having a small centralbore 50 extending an entire length of the shank 4 along the axis A. Thebore 50 is defined by an inner cylindrical wall of the shank 4 and has acircular opening at the shank tip 28 and an upper circular openingcommunicating with the external drive 46 at the driving seat 45. Thebore 50 is coaxial with the threaded body 6 and the upper portion orhead 8. The bore 50 provides a passage through the shank 4 interior fora length of wire (not shown) inserted into the vertebra 17 prior to theinsertion of the shank body 6, the wire providing a guide for insertionof the shank body 6 into the vertebra 17. It is foreseen that the shankcould be solid and made of different materials, including metal andnon-metals.

To provide a biologically active interface with the bone, the threadedshank body 6 may be coated, perforated, made porous or otherwisetreated. The treatment may include, but is not limited to a plasma spraycoating or other type of coating of a metal or, for example, a calciumphosphate; or a roughening, perforation or indentation in the shanksurface, such as by sputtering, sand blasting or acid etching, thatallows for bony ingrowth or ongrowth. Certain metal coatings act as ascaffold for bone ingrowth. Bio-ceramic calcium phosphate coatingsinclude, but are not limited to: alpha-tri-calcium phosphate andbeta-tri-calcium phosphate (Ca₃(PO₄)₂, tetra-calcium phosphate(Ca₄P₂O₉), amorphous calcium phosphate and hydroxyapatite(Ca₁₀(PO₄)₆(OH)₂). Coating with hydroxyapatite, for example, isdesirable as hydroxyapatite is chemically similar to bone with respectto mineral content and has been identified as being bioactive and thusnot only supportive of bone ingrowth, but actively taking part in bonebonding.

With particular reference to FIGS. 1 and 4-10, the receiver 10 has agenerally U-shaped appearance with partially discontinuous cylindricalinner and outer profiles as well as planar and other curved surfaces.The receiver 10 has an axis of rotation B that is shown in FIG. 1 asbeing aligned with and the same as the axis of rotation A of the shank4, such orientation being desirable, but not required during assembly ofthe receiver 10 with the shank 4. After the receiver 10 is pivotallyattached to the shank 4, either before or after the shank 4 is implantedin a vertebra 17, the axis B is typically disposed at an angle withrespect to the axis A, as shown, for example, in FIGS. 40-45.

The receiver 10 includes a base 60 with various curved surfaces 58,opposed outer planar surfaces 59, and opposed outer planar surfaces 59′,the base 60 defining a bore or inner cavity, generally 61, the base 60being integral with a pair of opposed upstanding arms 62. At the base60, the planar surfaces 59 are located between the arms 62 and an insetsurface portion 63 is located above and adjacent to each planar surface59, each inset surface portion 63 spanning between the pair of arms 62.The arms 62 form a cradle and define a U-shaped channel 64 between thearms 62 with an upper opening, generally 66, and a U-shaped lowerchannel portion or seat 68, the channel 64 having a width for operablysnugly receiving the rod 21 or portion of another longitudinal connector(or sleeve of a tensioned cord connecting member) between the arms 62,the channel 64 communicating with the base cavity 61. Inner opposedsubstantially planar arm surfaces 69 partially define the channel 64above the curved seat 68 and partially define outer sides of each arminterior surface generally 70, that includes various inner cylindricalprofiles, an upper one of which is a partial helically wound guide andadvancement structure 72 located adjacent top surfaces 73 of each of thearms 62. In the illustrated embodiment, the guide and advancementstructure 72 is a partial helically wound interlocking flange formconfigured to mate under rotation with a similar structure on theclosure structure 18, as described more fully below. However, it isforeseen that for certain embodiments of the invention, the guide andadvancement structure 72 could alternatively be a square-shaped thread,a buttress thread, a reverse angle thread or other thread-like ornon-thread-like helically wound discontinuous advancement structures,for operably guiding under rotation and advancing the closure structure18 downward between the arms 62, as well as eventual torquing when theclosure structure 18 abuts against the rod 21 or other longitudinalconnecting member. It is foreseen that the arms 62 could have break-offextensions.

An opposed pair of vertically extending outer grooves, generally 74,running substantially parallel to the receiver axis B are centrallyformed in outer curved convex surfaces 76 of the arms 62. Each groove 74runs centrally from the respective arm top surface 73 and terminates ata a lower through aperture 77. Each aperture 77 extends through therespective arm surface 77 to the respective inner arm surface 70 and islocated spaced from the receiver base 60. Each groove 74 has an upperopening partially defined by a pair of opposed surfaces 79 and 80 and asubstantially planar outer wall surface 81 extending between thesurfaces 79 and 80. The planar wall surface terminates at the top armsurface 73 and at a lower surface 82 partially defining the aperture 77.The opposed surfaces 79 and 80 are disposed at a slight angle withrespect to each other, forming the groove 74 as a dovetail-like spacefor easily receiving an elongate tool (not shown) that enters into thegroove 74 at the arm top surface 73 and is kept in close sliding contactwith the surface 81 by the orientation of the surfaces 79 and 80 anglingtoward one another with the tool sliding along the surface 81 andultimately into contact with winged portions of the insert 14 thatextend through the aperture 77 as will be described in greater detailbelow. At the through aperture 77, the dovetail surfaces 79 and 80terminate near facing generally c-shaped ears 83 that do not extendcompletely through the respective arm 62, but rather include a thin wallthat provides a crimping portion or wall 84. The crimping portions orwalls 84 are sized and shaped for pressing or crimping some or all ofthe wall material into grooves or arms surfaces adjacent to the wings ofthe insert 14 to prohibit rotation and misalignment of the insert 14with respect to the receiver 10 as will be described in greater detailbelow. In other embodiments of the invention, other surfaces at or nearthe grooves 74 may be inwardly crimped. The illustrated through aperture77 located below each grooves 74 is substantially the same width as thegroove 74 there-above, each aperture 77 being partially defined by apair of opposed side walls 86 and a bottom surface 87, resulting in theaperture 77 having a substantially rectangular profile. Each surface 87slants outwardly and downwardly from the inner arm surface 70 toward thereceiver base 60 outer planar surface 59′. The through apertures 77 aresized and shaped for receiving tooling and also the outer tangs of theretainer 12 during assembly as shown, for example, in FIG. 24.

The receiver 10 is a one-piece or integral structure and is devoid ofany spring tabs or collet-like structures. Preferably the insert and/orreceiver are configured with structure for blocking rotation of theinsert with respect to the receiver, such as the crimp walls 84, butallowing some up and down movement of the insert with respect to thereceiver during the assembly and implant procedure. Also formed in eachouter arm surface 76 near the top surface 73 is an undercut toolreceiving and engaging groove 89. Some or all of the apertures andgrooves described herein, including, but not limited to grooves 74,apertures 77, and grooves 89 may be used for holding the receiver 10during assembly with the insert 14, the retainer 12 and the shank 4;during the implantation of the shank body 6 into a vertebra when theshank is pre-assembled with the receiver 10; during assembly of the boneanchor assembly 1 with the rod 21 and the closure structure 18; andduring lock and release adjustment of insert embodiments according tothe invention with respect to the receiver 10, either into or out offrictional engagement with the inner surfaces of the receiver 10 as willbe described in greater detail below. It is foreseen that tool receivinggrooves or apertures may be configured in a variety of shapes and sizesand be disposed at other locations on the receiver arm 62 outer surfaces76 and/or inner surfaces 70 as well as the base 60 outer or innersurfaces.

Returning to the interior surface 70 of the receiver arms 62, locatedbelow the guide and advancement structure 72 is a discontinuouscylindrical surface 90 partially defining a run-out feature for theguide and advancement structure 72. Adjacent the surface 90 is a ledgeor upper annular surface 91 that in turn is adjacent to anothercylindrical surface 92 having a larger diameter than the cylindricalsurface 90. As best shown in FIG. 9, the upper annular surface 91includes the upper surface 82 that partially defines the aperture 77.The cylindrical surface 92 is sized and shaped to receive an upperwinged portion of the insert 14 as will be described in greater detailbelow. Therefore, the surface 92 has a diameter greater than a greaterdiameter of the guide and advancement structure 72. The receiver 10 mayfurther includes sloped, stepped or chamfered surfaces above and belowthe surface 92. The surface 92 is divided not only by the U-shapedchannel 64, but also by each of the through apertures 77, resulting inthe surface 92 being in four sections. At each aperture 77, the surface92 includes a surface portion 92′ that is located at the inside of ears83 of the crimping wall portions 84, the surface portions 92′ eventuallyin contact with the insert 14 as will be described below. A lower,substantially annular ledge 93 faces each upper ledge or annular surface91 and is adjacent the cylindrical surface 92. An inwardly anddownwardly sloping surface or chamfer 93′ is adjacent to each surface 93and also adjacent to another discontinuous cylindrical arm surface 94.Each cylindrical surface 94 has a diameter smaller than the surface 92and extends all the way down to the U-shaped channel seat 68. A portionof each aperture 77 extends through each surface 94. A lower partiallysloping or stepped ledge 94′ at the base of the cylindrical surface 92slopes downwardly toward the receiver base 60 and extends inwardlytoward the axis B, the surface 94 terminating at a cylindrical surface95 that extends completely around the receiver base 60 and thus runsbeneath each arm 62 and is adjacent to the lower seat 68. The innersurface 95 thus defines an upper and inner portion of the receiver base60. The cylindrical surface has a diameter slightly smaller than thediameter of the surface 94. The surface 95 terminates at a ledge surfaceor chamber ceiling 96 that extends outwardly away from the axis B, thesurface 96 being substantially perpendicular to the axis B, but could beoblique. The surface 96 is annular and defines an upper ceiling or stopof a retainer ring expansion portion or chamber of the inner cavity 61that is further defined by an adjacent outwardly sloping surface 97 anda cylindrical surface 98 that is adjacent the surface 97. The surface 97also acts as a stop for and slidingly cooperates with outwardly andupwardly projecting retainer tangs or panels as will be described ingreater detail below. The cylindrical surface 98 has a diameter greaterthan the diameter of the cylindrical surface 95. The cylindricalsurfaces 92, 95 and 98 are all centrally aligned with and run parallelto the receiver axis B. The surface 98 defines a circumferential recessthat is sized and shaped to receive the retainer 12 as it expands aroundthe shank upper portion 8 as the shank 8 moves upwardly toward thechannel 64 during assembly. It is foreseen that the recess could betapered or conical in configuration.

A pair of cylindrical surfaces 100 and 101 with an annular step surface102 therebetween as well as a lower annular step 103 located below andadjacent to the surface 101 provide a lower seat for the retainer 12 aswill be described in greater detail below. The surfaces 102 and 103 aresubstantially perpendicular to the surfaces 100 and 101 and the receiveraxis B. The surfaces 100, 101, 102 and 103 are located below thecylindrical surface 98 in the lower part of the base 60 and are sizedand shaped to closely receive and surround a lower base portion andlower skirt or sub-structure of the retainer 12 when the retainer is ina nominal or reduced deployment position as shown in FIGS. 35-37, forexample. Thus, the cylindrical surface 101 has a diameter smaller thanthe diameter of the cylindrical surface 98 that defines the expansionarea or expansion chamber for the retainer 12. The surface 101 is joinedor connected to the surface 98 by one or more beveled, curved or conicaltransition step surfaces 104. The surfaces 104 allow for sliding andnominal or deployment positioning of the retainer 12 into the spacedefined by the surfaces 100 and 101 and ultimate seating of the retainer12 on the lower substantially horizontal annular surfaces 102 and 103.

Located below and adjacent to the annular seating surface 103 is a loweredge or rim surface 106 that communicates with a beveled or flaredbottom opening surface 107, the surface 107 communicating with anexterior base or bottom surface 108 of the base 60, defining a loweropening, generally 110, into the base cavity 61 of the receiver 10. Insome embodiments of the invention, it is foreseen that one or morecurvate cut-out or cupped surfaces may be formed in a portion of thebase surface 108, as well as in portions of the surfaces 107, 106 and100-104, typically located substantially centrally and directly below anarm 62. Such a cupped surface may be sized and shaped for providingclearance for an increased angle of articulation between the shank 4 andthe receiver 10 (see, e.g., FIG. 55).

With particular reference to FIGS. 1 and 11-16, the lower open or splitfriction fit retainer 12, that operates to capture the shank upperportion 8 within the receiver 10 is shown. In certain stages of assemblyand operation, the retainer 12 is partially constrained within thereceiver, being captured within the receiver cavity 61 at a locationbelow the surface 96, the retainer 12 being rotatable with respect tothe receiver, but not pivotable thereto and not readily removable out ofthe receiver once deployed downward into the receiver cavity 61. Theretainer 12 has a central axis that is operationally the same as theaxis B associated with the receiver 10 when the shank upper portion 8and the retainer 12 are installed within the receiver 10. The retainer12 includes a substantially annular, cylindrical discontinuous body 115.Extending upwardly and outwardly from the body 115, and integralthereto, is a super-structure in the form of two sets of flexible panelsor tangs, in particular, inner panels or tangs 117 and outer panels ortangs 118, the panels 117 and 118 extending upwardly in aligned pairs,allowing for lateral spaces between the pairs panels or tangs to provideclearance during assembly of the retainer 12 with the receiver 10 innersurfaces (see, e.g., FIGS. 24 and 25). The illustrated embodimentincludes six pairs of inner and outer panels or tangs 117, 118, but itis foreseen that more or fewer panels or tangs may be used. The pairs ofpanels or tangs are generally equally spaced about the body 115. Alsointegral to the body 115 are six outer discontinuous cylindrical supportsurfaces 120, each surface 120 located beneath one of the outer panels118 and extending radially outwardly from the body 115. Below thesurfaces 120, the cylindrical body 115 forms a lower outer cylindricalskirt 121 broken only by a gap that will be described in greater detailbelow. The outer surface 121 is adjacent a bottom surface 122. The body115 also includes outer surface portions 123 that are located betweeneach outer panels 118 and support surfaces 120. The surface portions 123are illustrated as substantially planar, but may be cylindrical. At eachof the panels 118, a lower ledge surface 124 is adjacent to one of theouter support surfaces 120. Each lower ledge 124 spans between one ofthe surfaces 120 and the cylindrical skirt surface 121. The lower skirt121 and the ledge surfaces 124, as well as the surfaces 120 are receiverseating surfaces as will be described in greater detail below. In theillustrated embodiment, transition areas where the body 115 meets thepanels 117 and 118 or the retainer bottom 122 are curved or chamfered.Each body portion 123 is adjacent to a substantially planar body topsurface 126 that is substantially located between pairs of panels 117and 118 forming a planar surface with a trapezoidal profile and alsoincludes a narrow strip that runs between the inner panels 117 and theouter panels 118.

The inner panels or tangs 117 each include a substantially planar outersurface 128 and a concave inner surface 129, the surfaces 129 each beingpartially radiused and partially cylindrical, making up a discontinuouscurved surface sized and shaped for friction fit engagement with theshank head 8 as best shown in FIG. 35 and as will be described ingreater detail below. However, it is foreseen that the panel innersurfaces 129 may also be planar or include edges or other surfacesfeatures for gripping, but not locking the retainer 12 to the shank head8 during assembly and manipulation, but prior to locking of thepolyaxial mechanism of the bone screw assembly 1. The panels 117generally slant or curve inwardly towards the central axis of theretainer 12 and thus ultimately inwardly toward the shank head 8. Eachpanel 117 includes a top surface 130 that is substantially planar andruns substantially parallel to the bottom surface 122 when the retaineris in a neutral position such as that shown in FIG. 16.

The outer panels or tangs 118 each have a planar outer surface 132, aplanar inner surface 133 and a planar top surface 134 that slopes at anoblique angle with respect to the retainer bottom surface 122. Thesurfaces 134 are perpendicular to adjacent surfaces 132. The panels 118generally extend outwardly away from the panels 117 as well as outwardlyand upwardly from the central axis of the retainer body 115. Eachsurface 133 faces an outer surface 128 of one of the panels 117. Thebody top surface 126 is reduced to a narrow strip between each pair ofpanels 117 and 118. The panels or tangs 117 and 118 are resilient, thepanels being expandable about the shank head 8 and the panels 118 beingcompressible inwardly and resiliently holding against the receiver innersurfaces during shipping and certain assembly steps. The panels 118 thenreturn to an original or near original shape within the receiver cavity61, capturing the retainer 12 within the receiver 10, but still allowingfor rotation of the retainer 12 with respect to the receiver 10 aboutthe receiver central axis B.

The retainer ring 12 is made from a resilient material, such as astainless steel or titanium alloy, so that the retainer 12 body 115 maybe expanded and the tabs or panels 117 and 118 of the retainer may bemanipulated during various steps of assembly as will be described ingreater detail below. The retainer 12 has a central channel or hollowthrough bore, generally 141, that passes entirely through the retainer12 from the inner panel top surfaces 130 to the bottom surface 122 ofthe retainer body 115. Surfaces that define the channel or bore 141 atthe body 115 include a discontinuous inner lower frusto-conical surface143 adjacent to the retainer body bottom surface 122, a discontinuous,substantially cylindrical surface 145 adjacent the frusto-conicalsurface 143 and a discontinuous annular step 146 located adjacent thecylindrical surface 145, the surface 146 being substantially parallel tothe bottom surface 122 and extending between the surface 145 and a lowercylindrical portion 129′ of the inner surface 129 that partially formsthe inner panels 117. The surfaces 145 and 146 terminate and jointogether at an edge 147 that is positioned and configured to engage theshank surface 34 as will be described in greater detail below. The innercylindrical surface 129′ adjacent the step 146 forms a continuous innercylindrical wall except at a slit, generally 148 that runs through thebody 115. The slit 148 creates a split or open ring retainer 12, theslit cutting entirely through the retainer body 115. In someembodiments, such a slit may run at an angle obtuse to the bottomsurface 122. In the illustrated embodiment, the slit 148 runssubstantially perpendicular to the surfaces 122. The slit 148 isprimarily for expansion of the retainer 12 during pop-on or snap-onassembly with the shank head 8. However, the slit 148 also compressesduring assembly with the receiver 10 as will be described in greaterdetail below. The slit 148 extends between the body top surface 126 andthe bottom surface 122 and is located substantially centrally betweentwo pairs of panels 117 and 118. Furthermore, at the location of theslit 148, a curved concave, cut-out surface 149 is formed in the bottomsurface 122 and the frusto-conical surface 143. The cut-out surface 149also extends into the cylindrical surface 145 and removes a portion ofthe step 146 at either side of the slit 148. The surface 149 is radiusedor otherwise curved for engagement with the shank head 8 at the surface34 as will be described in greater detail below. In the illustratedembodiment, the cut-out surface 149 is located substantially equally oneither side of the slit 148 to provide for a desirable increased angleof orientation between the shank 8 and the retainer 12 and thus adesirable increased or extended angle of articulation between the shank8 and the receiver 10. The rotatability of the semi-constrained retainer12 with respect to the receiver 10 allows for manipulation and placementof such an increased angle of articulation to a location desired by asurgeon. The through slit 148 of the resilient retainer 12 is defined byfirst and second end surfaces, 152 and 153 disposed in substantiallyparallel spaced relation to one another when the retainer is in aneutral or nominal state. Both end surfaces 152 and 153 are disposedperpendicular to the bottom surface 122, but in some embodiments may bedisposed at an obtuse angle thereto. A width between the surfaces 152and 153 is narrow to provide stability to the retainer 12 duringoperation, but wide enough to allow for some compression of the retainerduring assembly as will be described in greater detail below. Becausethe retainer 12 is top loadable in a substantially neutral state andultimately expands during locking of the polyaxial mechanism, the widthof the slit 148 may be much smaller than might be required for a bottomloaded compressible retainer ring.

With particular reference to FIGS. 1 and 17-23, the locking compressioninsert 14 is illustrated that is sized and shaped to be received by anddown-loaded into the receiver 10 at the upper opening 66. Thecompression insert 14 has an operational central axis that is the sameas the central axis B of the receiver 10. In operation, the insertadvantageously frictionally engages the bone screw shank upper portion 8as well as engaging the receiver 10 in an interference fit engagement,locking the shank 4 in a desired angular position with respect to thereceiver 10 that remains in such locked position even if, for example, arod and closure top are later removed and the rod is replaced withanother rod or other longitudinal connecting member or member component,such as a sleeve of a tensioned cord connecting member. Such lockedposition may also be released by the surgeon if desired with insertengaging tools (not shown). As will be described in greater detail belowwith respect to the alternative insert 14″ shown in FIGS. 57-59, in someembodiments of the invention, the insert does not have the receiverinterference fit feature. The locking insert 14, the non-locking insert14″ and an alternative locking insert 14′ for use with a deformable rod(shown in FIGS. 38 and 39) are preferably made from a solid resilientmaterial, such as a stainless steel or titanium alloy, so that portionsof the insert may be grasped, pinched or pressed, if necessary, andun-wedged from the receiver 10 with a release tool (not shown).

The locking compression insert 14 includes a body 156 with cylindricalsurfaces of a variety of diameters, the body 156 being integral with apair of upstanding arms 157. Located between the arms 157, the body 156has an outer partial cylindrical surface 158. Located beneath eachupstanding arm 157 is a discontinuous, cylindrical, interference fitsurface or band 159 that extends outwardly from an arm and body outersubstantially cylindrical surface 160, a diameter of the surface 159being larger than a diameter of the surface 160. Beneath each surface159 is a discontinuous cylindrical surface 161 having a diameter thesame or similar to the surface 160. A lower ledge surface 162 spansbetween each surface 159 and the corresponding lower cylindrical surface161. The lower surface 161 is adjacent to a chamfered surface 163 thatis in turn adjacent a substantially planar and annular bottom surface164.

The insert 14 further includes substantially planar arm top surfaces 165located opposite the bottom surface 164. Adjacent the top surfaces 165of the arms 157 are opposed inwardly facing cut-outs or grooved surfaces167. The arms 157 are sized and configured for ultimate placement at orbeneath the cylindrical run-out surface 90 located below the receiverguide and advancement structure 72. The grooves or apertures 167 provideholding surfaces for tools and also provide some clearance between theclosure top 18 and the insert 14 when both are within the cylindricalrun-out surface 90 of the receiver so that the closure top 18frictionally engages the rod 21 only, pressing the rod 21 downwardlyagainst the insert 14 that in turn presses against the shank 4 upperportion 8 that presses against the retainer 12 to lock the polyaxialmechanism of the bone screw assembly 1 at a desired angle. Additionally,the grooves 167 may be sized and shaped to cooperate with protrusions orextensions on sleeves that cooperate with a tensioned cord of alongitudinal connecting member assembly to center such a sleeve withinthe bone screw assembly 1.

An alternative locking insert 14′ shown in FIGS. 38 and 39 includes allthe features of the insert 14 with the exception of the grooves 167. Topsurfaces 165′ of the insert 14′ that have more surface area than thesurfaces 165 of the insert 14 directly engage the alternative closuretop 18′ for better locking of the polyaxial mechanism when analternative deformable rod 21′ is being captured between the insert 14′and the closure top 18′.

Returning to the insert 14 shown in FIGS. 17-23, located on the arms 157and extending outwardly from each surface 160 at a location spaced fromthe top surfaces 165 are a pair of opposed extensions or wings 168. Thewings 168 are partially defined by upper surfaces 169, by outerpartially cylindrical surfaces 170 and by lower surfaces 171, the uppersurfaces 169 and the lower surfaces 171 being substantially parallel toon another. Opposed side surfaces 172 span between top and bottomsurfaces 169 and 171 respectively, of each wing 168, the side surfaces172 being substantially perpendicular to adjacent top and bottomsurfaces 169 and 171. The cylindrical surfaces 170 are sized and shapedfor sliding rotation within the receiver arm cylindrical surfaces 92during assembly of the insert 14 with the receiver 10 as will bedescribed in greater detail below.

Returning to the inner surfaces of the insert 14, a through bore,generally 173, is disposed primarily within and through the body 156 andcommunicates with a generally U-shaped through channel formed by asaddle surface 174 that is substantially defined by the upstanding arms157. Near the top surfaces 165, the saddle surface 174 is substantiallyplanar, with the apertures 167 extending thereinto. The saddle 174 has alower seat 175 sized and shaped to closely, snugly engage the rod 21 orother longitudinal connecting member. It is foreseen that an alternativeembodiment may be configured to include planar holding surfaces thatclosely hold a square or rectangular bar as well as hold a cylindricalrod-shaped, cord, or sleeved tensioned cord longitudinal connectingmember. A second set of opposed, inwardly facing apertures 176 arelocated in the saddle 174 near the lower seat 175 and substantiallydirectly below, but spaced from, the upper grooves or apertures 167. Thegrooves 176 are sized and shaped to receive tooling for rotation andother manipulation of the insert 14.

The bore, generally 173, is substantially defined at the body 156 by aninner cylindrical surface 177 that communicates with the seat 175 andalso communicates with a lower concave, radiused or otherwise curvedportion 178 having shank gripping surfaces or ridges 180, the portion178 generally having a radius for closely mating with the surface 34 ofthe shank upper portion 8. The portion 178 terminates at the basesurface 164. In some embodiments of the invention, the gripping surfacesor ridges 180 are located near the cylindrical surface 177 and a lowerpart of the portion 178 is a smooth, radiused or spherical surface. Inthe illustrated embodiment, the gripping ridges or steps 180 are sizedand shaped to grip and penetrate into the shank head 8 when the insert14 is locked against the head surface 34. It is foreseen that there maybe more or fewer steps or ridges 180. It is foreseen that the grippingridges 180 as well as a remainder of the lower shank engaging portion178 may additionally or alternatively include a roughened or texturedsurface or surface finish, or may be scored, knurled, or the like, forenhancing frictional engagement with the shank upper portion 8.

The compression insert 14 through bore 173 is sized and shaped toreceive a driving tool (not shown) therethrough that engages the shankdrive feature 46 when the shank body 6 is driven into bone with thereceiver 10 attached. Also, in some locking embodiments of theinvention, the bore receives a manipulation tool (not shown) used forreleasing the insert from a locked position with the receiver, the toolpressing down on the shank and also gripping the insert at the apertures176 and/or 167, or with other tool engaging features. Each of the arms157 and the insert body 156 may include more surface features, such ascut-outs notches, bevels, etc. to provide adequate clearance forinserting the insert 14 into the receiver and cooperating with theretainer 12 during the different assembly steps as will be described ingreater detail below.

The insert body 156 cylindrical surface 158 has a diameter slightlysmaller than a diameter between crests of the guide and advancementstructure 72 of the receiver 10, allowing for top loading of thecompression insert 14 into the receiver opening 66, with the arms 157 ofthe insert 14 being located between the receiver arms 62 duringinsertion of the insert 14 into the receiver 10. Once the arms 157 ofthe insert 14 are generally located beneath the guide and advancementstructure 72, the insert 14 is rotated into place about the receiveraxis B with the wings 168 entering the receiver groove formed by thecylindrical surface 92, the adjacent upper annular surface 91 and theadjacent lower annular surface 93 until the wings are located in theapertures 77 as will be described in greater detail below.

With reference to FIGS. 1 and 35-37, the illustrated elongate rod orlongitudinal connecting member 21 (of which only a portion has beenshown) can be any of a variety of implants utilized in reconstructivespinal surgery, but is typically a cylindrical, elongate structurehaving the outer substantially smooth, cylindrical surface 22 of uniformdiameter. The rod 21 may be made from a variety of metals, metal alloys,non-metals and deformable and less compressible plastics, including, butnot limited to rods made of elastomeric, polyetheretherketone (PEEK) andother types of materials, such as polycarbonate urethanes (PCU) andpolyethelenes.

Longitudinal connecting members for use with the assembly 1 may take avariety of shapes, including but not limited to rods or bars of oval,rectangular or other curved or polygonal cross-section. The shape of theinsert 14 may be modified so as to closely hold the particularlongitudinal connecting member used in the assembly 1. Some embodimentsof the assembly 1 may also be used with a tensioned cord. Such a cordmay be made from a variety of materials, including polyester or otherplastic fibers, strands or threads, such as polyethylene-terephthalate.Furthermore, the longitudinal connector may be a component of a longeroverall dynamic stabilization connecting member, with cylindrical orbar-shaped portions sized and shaped for being received by thecompression insert 14 of the receiver having a U-shaped, rectangular- orother-shaped channel, for closely receiving the longitudinal connectingmember. The longitudinal connecting member may be integral or otherwisefixed to a bendable or damping component that is sized and shaped to belocated between adjacent pairs of bone screw assemblies 1, for example.A damping component or bumper may be attached to the longitudinalconnecting member at one or both sides of the bone screw assembly 1. Arod or bar (or rod or bar component) of a longitudinal connecting membermay be made of a variety of materials ranging from deformable plasticsto hard metals, depending upon the desired application. Thus, bars androds may be made of materials including, but not limited to metal andmetal alloys including but not limited to stainless steel, titanium,titanium alloys and cobalt chrome; or other suitable materials,including plastic polymers such as polyetheretherketone (PEEK),ultra-high-molecular weight-polyethylene (UHMWP), polyurethanes andcomposites, including composites containing carbon fiber, natural orsynthetic elastomers such as polyisoprene (natural rubber), andsynthetic polymers, copolymers, and thermoplastic elastomers, forexample, polyurethane elastomers such as polycarbonate-urethaneelastomers.

With reference to FIGS. 1 and 35-37, the closure structure or closuretop 18 shown with the assembly 1 is rotatably received between thespaced arms 62 of the receiver 10. It is noted that the closure 18 topcould be a twist-in or slide-in closure structure. The illustratedclosure structure 18 is substantially cylindrical and includes a anouter helically wound guide and advancement structure 182 in the form ofa flange that operably joins with the guide and advancement structure 72disposed on the arms 62 of the receiver 10. The flange form utilized inembodiments according to the present invention may take a variety offorms, including those described in Applicant's U.S. Pat. No. 6,726,689,which is incorporated herein by reference. Although it is foreseen thatthe closure structure guide and advancement structure couldalternatively be a buttress thread, a square thread, a reverse anglethread or other thread like or non-thread like helically woundadvancement structure, for operably guiding under rotation and advancingthe closure structure 18 downward between the arms 62 and having such anature as to resist splaying of the arms 62 when the closure structure18 is advanced into the channel 64, the flange form illustrated hereinas described more fully in Applicant's U.S. Pat. No. 6,726,689 ispreferred as the added strength provided by such flange formbeneficially cooperates with and counters any reduction in strengthcaused by the any reduced profile of the receiver 10 that may moreadvantageously engage longitudinal connecting member components. Theillustrated closure structure 18 also includes a top surface 184 with aninternal drive 186 in the form of an aperture that is illustrated as astar-shaped internal drive such as that sold under the trademark TORX,or may be, for example, a hex-shaped drive or other internal drives suchas slotted, tri-wing, spanner, two or more apertures of various shapes,and the like. A driving tool (not shown) sized and shaped for engagementwith the internal drive 186 is used for both rotatable engagement and,if needed, disengagement of the closure 18 from the receiver arms 62. Itis also foreseen that the closure structure 18 may alternatively includea break-off head designed to allow such a head to break from a base ofthe closure at a preselected torque, for example, 70 to 140 inch pounds.Such a closure structure would also include a base having an internaldrive to be used for closure removal. A base or bottom surface 188 ofthe closure is planar and further includes a rim 190 for engagement andpenetration into the surface 22 of the rod 21 in certain embodiments ofthe invention. It is noted that in some embodiments, the closure topbottom surface 188 may further include a central point for penetrationinto the rod. It is also noted that other embodiments may or may notinclude the point and/or the rim. The closure top 18 may further includea cannulation through bore (not shown) extending along a central axisthereof and through the top and bottom surfaces thereof. Such a throughbore provides a passage through the closure 18 interior for a length ofwire (not shown) inserted therein to provide a guide for insertion ofthe closure top into the receiver arms 62.

An alternative closure top, such as the top 18′ shown in FIGS. 38 and 39for use with a deformable rod, such as a PEEK rod 21′, for example,includes a bottom surface 188′ that has domed portion 190′ with acentral nub 189′ in lieu of the point and rim surface of the closure top18. Otherwise, the closure top 18′ includes a guide and advancementstructure 182′, a top surface 184′ and an internal drive feature 186′the same or substantially similar to the respective guide andadvancement structure 182, top surface 184 and internal drive feature186 of the closure top 18.

The assembly 1 receiver 10, retainer 12 and compression insert 14 aretypically assembled at a factory setting that includes tooling forholding and alignment of the component pieces and manipulating theretainer 12 and the insert 14 with respect to the receiver 10. In somecircumstances, the shank 4 is also assembled with the receiver 10, theretainer 12 and the compression insert 14 at the factory. In otherinstances, it is desirable to first implant the shank 4, followed byaddition of the pre-assembled receiver, retainer and compression insertat the insertion point. In this way, the surgeon may advantageously andmore easily implant and manipulate the shanks 4, distract or compressthe vertebrae with the shanks and work around the shank upper portionsor heads without the cooperating receivers being in the way. In otherinstances, it is desirable for the surgical staff to pre-assemble ashank of a desired size and/or variety (e.g., surface treatment ofroughening the upper portion 8 and/or hydroxyapatite on the shank 6),with the receiver, retainer and compression insert. Allowing the surgeonto choose the appropriately sized or treated shank 4 advantageouslyreduces inventory requirements, thus reducing overall cost and improvinglogistics and distribution.

Pre-assembly of the receiver 10, retainer 12 and compression insert 14is shown in FIGS. 24-30. With particular reference to FIG. 24, first theretainer 12 is inserted into the upper receiver opening 66, leading withthe outer panels 118 with the panel 118 top surfaces 134 facing one arm62 and the retainer bottom surface 122 facing the opposing arm 62 (shownin phantom). The retainer 12 is then lowered in such sideways mannerinto the channel 64 and partially into the receiver cavity 61, followedby tilting the retainer 12 such that at least one outer panel 118 isreceived into one of the apertures 77 and the opposed panel 118 islocated beneath the guide and advancement structure 72. Then, withreference to FIG. 25, the retainer 12 is tilted into a position whereinthe central axis of the retainer 12 is generally aligned with thereceiver central axis B. As shown in FIG. 25, the retainer outersurfaces 120 engage the receiver inner cylindrical surface 95 and theretainer slit 148 is reduced such that the surfaces 152 and 153 thatdefine the slit 148 are touching or almost touching as shown in FIG. 26while the surfaces 120 are slid past the receiver surface 95. Withreference to FIG. 27, the retainer 12 is pressed downwardly into thereceiver to a location wherein the outer tangs 118 resiliently pressagainst the receiver surface 95, holding the retainer within thereceiver cavity 61 at a desired temporary position, but not allowing theretainer 12 to drop downwardly onto the receiver seating transitionsurfaces 104. At this time, the retainer 12 is not yet fully capturedwithin the receiver base cavity 61, but cannot be readily removed unlessthe panels 118 are squeezed toward one another using a tool or tools.

With further reference to FIG. 27 and with reference to FIGS. 28 and 29,the compression insert 14 is then downloaded into the receiver 10through the upper opening 66 with the bottom surface 164 facing thereceiver arm top surfaces 73 and the insert arm outer surfaces 160located between the opposed receiver arms 62. The insert 14 is thenlowered toward the receiver base 60 until the insert 14 arm uppersurfaces 165 are adjacent the run-out area below the guide andadvancement structure 72 defined in part by the cylindrical surface 92and the wings 168 are generally aligned with the receiver groove definedin part by the cylindrical surface 92. Thereafter, the insert 14 isrotated about the receiver axis B until the upper arm surfaces 165 aredirectly below the guide and advancement structure 72 with the U-shapedchannel 173 of the insert 14 aligned with the U-shaped channel 64 of thereceiver 10 and the insert wings 168 located at the apertures 77. Insome embodiments, the insert arms may need to be compressed slightlyduring rotation to clear some of the inner surfaces 70 of the receiverarms 62. With particular reference to FIG. 30, at this time, the fourcrimping wall portions 84 are pressed inwardly towards the insert 14 ateither side 172 of each wing 168, the crimping wall material pressingagainst the insert 14 near the wing sides 172 and thereby prohibitingthe insert 14 from rotating with respect to the receiver axis B. At thistime, there can be some upward and downward movement of the insert 14,but such movement is limited as the upper wall 82 defining the receiveraperture 77 stops further upward movement of the insert wings 168 andthe retainer outer tang top surfaces 134 stop downward movement of thenow trapped insert 14. Thus, the frictional engagement between the tangsor panels 118 and the receiver inner surfaces 95 prohibit the retainer12 and also the insert 14 from dropping further down into the receiver10 cavity 61. The retainer 12 and the insert 14 are now in a desiredposition for shipping as an assembly along with the separate shank 4.

Typically, the receiver and retainer combination are shipped orotherwise provided to the end user with the spring-like tangs 118 wedgedagainst the receiver as shown in FIG. 32. The receiver 10, retainer 12and insert 14 combination is now pre-assembled and ready for assemblywith the shank 4 either at the factory, by surgery staff prior toimplantation, or directly upon an implanted shank 4 as will be describedherein.

As illustrated in FIG. 31, the bone screw shank 4 or an entire assembly1 made up of the assembled shank 4, receiver 10, retainer 12 andcompression insert 14, is screwed into a bone, such as the vertebra 17(shown in phantom), by rotation of the shank 4 using a suitable drivingtool (not shown) that operably drives and rotates the shank body 6 byengagement thereof at the internal drive 46. Specifically, the vertebra17 may be pre-drilled to minimize stressing the bone and have a guidewire (not shown) inserted therein to provide a guide for the placementand angle of the shank 4 with respect to the vertebra. A further taphole may be made using a tap with the guide wire as a guide. Then, thebone screw shank 4 or the entire assembly 1 is threaded onto the guidewire utilizing the cannulation bore 50 by first threading the wire intothe opening at the bottom 28 and then out of the top opening at thedrive feature 46. The shank 4 is then driven into the vertebra using thewire as a placement guide. It is foreseen that the shank and other bonescrew assembly parts, the rod 21 (also having a central lumen in someembodiments) and the closure top 18 (also with a central bore) can beinserted in a percutaneous or minimally invasive surgical manner,utilizing guide wires and attachable tower tools mating with thereceiver. When the shank 4 is driven into the vertebra 17 without theremainder of the assembly 1, the shank 4 may either be driven to adesired final location or may be driven to a location slightly above orproud to provide for ease in assembly with the pre-assembled receiver,compression insert and retainer.

With reference to FIG. 32, the pre-assembled receiver, insert andretainer are placed above the shank upper portion 8 until the shankupper portion is received within the opening 110. With particularreference to FIGS. 32-37, as the shank upper portion 8 is moved into theinterior 61 of the receiver base, the shank upper portion 8 pressesupwardly against the retainer 12 in the receiver recess partiallydefined by the cylindrical surface 98, specifically the surface portions120 press against the surface 98 as the retainer 12 expands about theshank 8. As the shank head 8 continues to move upwardly toward thechannel 64, the shank head surface 34 also forces the retainer 12against the insert 14. However, the insert 14 is prohibited from movingupward by the wing upper surfaces 169 abutting against the surfaces 82(that is also the ceiling annular surface 91 adjacent the groove 92)defining the apertures 77. Therefore, the upwardly moving shank head 8forces a widening of the retainer slit 148 and corresponding outwardmovement of the body 115 of the retainer 12 towards the receivercylindrical surfaces 98 and stepped or curved surface 104 defining thereceiver expansion recess or chamber as best shown in FIG. 33, while theretainer tangs 118 near the top surfaces 134 thereof are generallymaintained in a location below the insert 14 bottom surface 164, withthe tangs 118 being pressed inwardly toward the axis B at thetermination of the receiver wall surface 95. At this time, the sphericalsurface 34 of the head 8 comes into contact with the retainer innercylindrical body 145 and the edge 147. With reference to FIG. 34, theretainer 12 begins to return towards a neutral or nominal state as thecenter of the sphere of the shank head 8 passes beyond the retainerinner edge 147. By the time the hemisphere of the spherical surface 34extends into a desired captured location within the retainer centralbore 141, the shank surface 34 is in contact with the edge 147 as wellas with the inner panels 117 at surfaces 129. The combination of the rimor edge 147 surface contact and the panel 117 surfaces 129 contactresiliently pressing against the radiused surface 34, provides a fairlytight friction fit between the head 8 and the retainer 12, the surface34 being pivotable with respect to the retainer 12 with some force.Thus, a tight, non-floppy ball and socket joint is now created betweenthe retainer 12 and the shank upper portion 8.

With reference to FIG. 35, the receiver is then pulled upwardly or theshank 4 and attached retainer 12 are then moved manually downwardly intoa position wherein the retainer tangs 118 are disengaged from thereceiver surfaces 95, allowing the tangs 118 to resiliently release andextend outwardly into a neutral or near-neutral position at a locationbelow the receiver annular surface 96 that defines the ceiling of thereceiver inner chamber 61. The tangs 118 are now captured within thereceiver. Any upward movement of the retainer 12 results in the tang topsurfaces 134 abutting against the receiver surfaces 96 and/or 97.However, although fully capture, the retainer 12/shank 4 combination isadvantageously only partially restrained with respect to the receiver10, as a user is able to rotate the retainer 12 about the receiver axisB prior to final locking of the shank head 8 with respect to thereceiver 10. At this time also, the retainer surface 121 and bottomsurface 122 that forms a lower skirt beneath the retainer body surfaces120 and 124 are all seated within the stepped surfaces of the receiver.Specifically, the retainer lower surfaces 124 are seated on the receiverannular surface 102 and the bottom surface 122 is seated on the annularsurface 103. Downward pressure of the shank head 8 on the retainer edge147 further expands the retainer body 115 outwardly, with the outersurfaces 120 pressing against the receiver inner cylindrical surface 100and the lower skirt surface 121 pressing against the receiver innercylindrical surface 101. The retainer body formed in part by the lowerskirt surface 121 advantageously allows for the head 8 to seat lowerwithin the receiver than in other known polyaxial bone anchors. As willbe described in greater detail below, the skirt feature that allows fora more stable lower seating surface in combination with the retainercupped surface 149 that allows for a favored increased or extendedangular orientation of the shank with respect to the retainer, and thuswith respect to the entire bone screw assembly, allows for such anangular increase without the need to provide a cut-out or cupped surfaceat and near the receiver bottom 108. Also advantageous is the fact thatthe partially constrained retainer 12 may be rotated with respect to thereceiver 10 about the axis B, allowing for the user to choose thelocation of the increased angle of orientation between the receiver 10and the shank 4.

With further reference to FIG. 35, after the retainer 12 is moveddownwardly into the receiver 10 and seated on the surfaces 102 and 103,the insert 14 remains located spaced above the shank head 8 as the outersurfaces 159 rest upon the receiver cylindrical surfaces 95, prohibitingdownward movement of the insert 14 unless a downward force is applied onthe insert either by a tool or the rod 21 and closure top 18, also shownin FIG. 35, for example. It is noted that FIG. 36 simply illustrates theextent of movement of the shank 4 if the shank would be pressed upwardlyinto the receiver during this stage of assembly. In such case, theretainer 12 would remain in a relatively fixed position due to the outertangs 118 being blocked from upward movement by the receiver ceilingsurface 96. The shank head 8 would abut against the insert 14 at thesurface 178 and gripping ridges 180, but the inner tangs 117 wouldcontinue to grip the shank spherical surface 34, so a friction fit wouldstill be possible, even if the shank gets moved upwardly. With referenceto FIG. 37, downward movement of the closure top 18 presses the rod 21downwardly that in turn pressed the insert 14 (and possibly the shank 4)downwardly into locking engagement with the retainer 12.

In some embodiments, when the receiver 10 is pre-assembled with theshank 4, the entire assembly 1 may be implanted by inserting the drivingtool (not shown) into the receiver and the shank drive 46 and rotatingand driving the shank 4 into a desired location of the vertebra 17. Atsuch time, prior to locking with a closure top, the receiver 10 may bearticulated to a desired angular position with respect to the shank 4(such as the angular orientations shown in FIGS. 40-45, for example),that will be held, but not locked, by the frictional engagement betweenthe retainer 12 inner tangs 117 and the shank upper portion 8. In somecases it may be desirable to lock the insert 14 into the receiver 10 atthis time, the insert 14 being pressed downwardly into lockingengagement with the shank head 8 by a tool pressing downwardly on theinsert, for example, with a tool (not shown) entering through thereceiver outer grooves 74 and pressing downwardly on the insert wings168. Such a tool may also include (or alternatively be) a structure forgripping the receiver, for example, a pronged tool or tool portion withsome of the tool extending into the receiver channel 64. Or, asexplained above, the insert 14 may remain spaced above the shank head 8until locked into place by the rod 21 and the closure top 18 pressingdown upon the insert 14.

As explained above and as best shown in FIGS. 35 and 37, the diameter ofthe insert outer surface or band 159 is sized large enough to requirethat the surface 159 must be forced into the cylindrical surface 95 ofthe receiver by a tool or tools or by the closure top 18 forcing the rod21 downwardly against the insert 14 with sufficient force tointerferingly frictionally lock or wedge the insert 14 into the receiver10 at the surface 159. This independent lock-and-release feature givesthe surgeon flexibility to loosen the closure top and even remove theclosure top and rod without affecting the locking of the polyaxialmechanism of the assembly 1, the anchor assembly functioning like afixed monoaxial screw with the shank 4 in fixed relation with thereceiver 10, but with the shank remaining in a desired angle withrespect to the receiver. Thus, once a locking insert is in aninterference fit locking engagement with the receiver as shown in FIG.37, if a rod and closure top have been assembled with the receiver 10,the closure top 18 may be loosened or removed and/or the rod 21 may beadjusted and/or removed and the frictional engagement between the insert14 and the receiver 10 at the receiver surface 95 will remain locked inplace, advantageously maintaining a locked angular position of the shank4 with respect to the receiver 10. At such time, another rod, such as adeformable rod 21′ and cooperating alternative closure top 18′ may beloaded onto the already locked-up assembly to result in an alternativeassembly.

With reference to FIGS. 38 and 39, there is illustrated an alternativeinsert 14′ that is identical to the insert 14 with the exception that anupper surface 165′ is sized and shaped for direct engagement with thealternative closure top 18′. The illustrated rod 21′ has the same orsimilar dimensions as the rod 21, with a cylindrical surface 22′, but ismade from a material, such as PEEK, that deforms in response to pressurefrom the closure top, thus making the closure top 18′ having the domedsurface 190′ and central nub 189′ a more desirable locking mechanism forkeeping the deformable rod 18′ in place within the receiver 10. Becausethe locking of the polyaxial mechanism of the assembly is not dependenton the force of the rod 21′ and closure top 18′ on the insert 14, anyfurther deformation or eventual loosening of the rod with respect to theclosure top 18′ or the insert 14 does not affect the secure lockingbetween the insert 14 and the receiver 10 and thus the shank 4 staysfrictionally locked against both the insert 14 and the retainer 12,locking the shank 4 in a desired angular position with respect to thereceiver 10.

If unlocking of the insert 14 or 14′ with respect to the receiver 10 isdesired, a tool (not shown) may be inserted into the through apertures77 below the insert wings 168 and the insert 14 or 14′ may be pulledaway from the receiver 10. Such a tool may include a piston-like portionfor pushing directly on the shank while the insert 14 is pulled awayfrom the receiver. At such time, the shank 4 may be articulated withrespect to the receiver 10, and the desired friction fit returns betweenthe retainer 12 and the shank surface 34, so that an adjustable, butnon-floppy relationship still exists between the shank 4 and thereceiver 10. If further disassembly if the assembly is desired, such isaccomplished in reverse order to the procedure described previouslyherein for the assembly 1.

Returning to FIGS. 35 and 36, the rod 21 is positioned in an open orpercutaneous manner in cooperation with the at least two bone screwassemblies 1. The closure structure 18 is then advanced between the arms62 of each of the receivers 10. The closure structure 18 is rotated,using a tool engaged with the inner drive 186 until a selected pressureis reached at which point the rod 21 engages the U-shaped saddle 173 ofthe compression insert 14, further pressing the insert spherical surface178 and stepped shank gripping surfaces 180 against the shank sphericalsurface 34, the edges 180 penetrating into the spherical surface 34,pressing the shank upper portion 8 into locked frictional engagementwith the retainer 12. Specifically, as the closure structure 18 rotatesand moves downwardly into the respective receiver 10, the rim 190 engageand penetrate the rod surface 22, the closure structure 18 pressingdownwardly against and biasing the rod 21 into compressive engagementwith the insert 14 that urges the shank upper portion 8 toward theretainer 12 and into locking engagement therewith at the retainer edgesurface 147, the retainer 12 frictionally abutting the receiver surfaces102 and 103 and pressing outwardly against the receiver cylindricalsurfaces 100 and 101. For example, about 80 to about 120 inch pounds oftorque on the closure top may be applied for fixing the bone screw shank6 with respect to the receiver 10. At this time, the retainer inner edge147 engages and digs into the shank head 8. At this time, the innertangs 117 may be slightly spaced from the shank head 8 or may be stilltouching the shank spherical surface 34, but are no longer in tight orclose frictional engagement with the surface 34 and thus are notparticipating in the final locking engagement between the shank 4 andthe retainer 12. As best shown in FIG. 37, due to the position andgeometry of the lower skirt surfaces 121 and 122 with respect to thereceiver 10 and also due to the location of the inner edge 147, theshank head 8 sits low in the receiver cavity 61, allowing for desirableincreased articulation of the shank 4 with respect to the retainer 12and thus with respect to the receiver 10 as compared to a retainer thatdoes not include such a lower skirt, for example. If disassembly if theassembly 1 is desired, such is accomplished in reverse order to theprocedure described previously herein for assembly.

With reference to FIGS. 40-45, different angular or articulatedpositions of the shank 4 with respect to the receiver 10 are shown, somemaking full use of the slit 148 and adjacent cut-out or cupped surfaces149 of the retainer 12. For example, compare FIGS. 43-45 wherein theshank 8 is pivoted toward and into engagement with the cupped surfaces149 as compared to the arrangement shown in FIGS. 40-42, wherein theshank 4 is pivoted in a direction opposite to the retainer slit 148. InFIGS. 40-42 wherein the shank is pivoted in a direction away from theslit 148 and cupped surfaces 149, a resulting shank to receiverarticulation is about eighteen degrees (cephalad, for example), which isa desirable degree of articulation in some instances. FIGS. 43-45 show athirty degree (caudad) or slightly further articulation, possible whenthe shank head 8 abuts against both surfaces 149 as well as movingslightly into the gap formed by the slit 148.

FIGS. 46-50 illustrate an alternative retainer 12′ that includes cuppedor cut-out surfaces 149′ that are graduated or stepped as compared tothe smooth surfaces 149 of the retainer 12. Otherwise, the retainer 12′is identical or substantially similar in form and function to theretainer 12 previously discussed herein. Thus, the retainer 12′ fullycooperates with the receiver 10, insert 14, shank 4, rod 21 and closuretop 18 in a manner substantially identical to what has been describedabove with respect to the assembly 1, with the exception that thestepped surfaces 149′ grip or dig into the shank 4 at the neck 26 whenthe shank is pivoted to an about thirty degree articulation with respectto the receiver as shown in FIG. 50. It is foreseen that greater orfewer stepped surfaces may be included along the cupped surface portion149′.

FIGS. 51-54 illustrate an alternative receiver 10′ that includes abottom surface 108′ further defined by a pair of opposed, concave curvedbottom surfaces 109′. Otherwise, the receiver 10′ is identical to thereceiver 10 described above and thus fully cooperates with the retainer12, insert 14, shank 4, rod 21 and closure top 18 in a mannersubstantially identical to what has been described above with respect tothe assembly 1. FIGS. 55-56 illustrate another alternative receiver 10″that is substantially similar to the receiver 10′, also having opposed,concave curved bottom surfaces 109″. The receiver 10″ differs from thereceiver 10′ only in that the surfaces 109″ are graduated or stepped.Just like the receiver 10, when the retainer 12 is fully assembled withthe receiver 10′ or the receiver 10″, the retainer 12 is captured withinthe receiver inner cavity, but is only partially constrained therein,the retainer being rotatable about the central axis of the receiver 10′or 10″. Thus, the retainer 12 slit 148 and surfaces 149 can be alignedwith either of the receiver concave surfaces 109′ or 109″. When theretainer surfaces 149 are aligned with one of the surfaces 109′ or 109″,at least a forty degree angle of articulation between the shank 4 andthe receiver 10′ or 10″ is possible.

With reference to FIGS. 57-59, an alternative non locking compressioninsert 14′ is illustrated for use with the shank 4, receiver 10,retainer 12, closure top 18 and rod 21 previously described herein. Theinsert 214 is substantially similar to the insert 14 previouslydescribed herein, having all the features of the insert 14 with theexception of the through apertures 167 and the enlarged interference fitsurface 159. Instead, the insert includes an other lower surface or band159″ having a diameter sized to easily slidingly fit within the receiversurface 95 rather than interferingly fit with such surface. The insert14″ is assembled with the receiver 10, retainer 12, shank 4, rod 21 andclosure top 18 in a manner the same as previously described above withrespect to the assembly 1, with the exception that the insert 14″ neednot be forced downwardly into a locking interference fit with thereceiver 10 when the shank 4 is locked in place. If the closure top 18is loosened or if the closure top 18 and the rod 21 are removed from theassembly 1, the insert 14″ will also shift upwardly in the receiver 10and the shank 4 will not remain locked with respect to the retainer 12and the receiver 10. Tooling (not shown) cooperating with the receivergrooves 74 to press downwardly on wings 168″ of the insert 14″advantageously provides for a temporary locking of the polyaxialmechanism during surgery, if desired by the surgeon.

It is to be understood that while certain forms of the present inventionhave been illustrated and described herein, it is not to be limited tothe specific forms or arrangement of parts described and shown.

What is claimed and desired to be secured by Letters Patent is asfollows:
 1. In a polyaxial pedicle screw including a shank having a bodyfor fixation to a bone and an integral upper portion, an U-shapedreceiver having a top portion and an integral base, the receiver topportion defining an open rod-receiving channel, the base defining acavity communicating with a bottom opening, the upper portion of theshank positionable within the cavity, and the channel communicating withthe cavity, the improvement comprising: a) a retainer positioned withinthe cavity prior to the shank being loaded and capturing the shank upperportion once loaded, the retainer being in a non-pivotal relationshipwith respect to the receiver; and wherein b) the retainer furtherincludes a cut-out surface being sized and shaped to provide forincreased polyaxial motion in at least one direction for the shank withrespect to the receiver.